1. Field of the Technology
The present invention relates to multimedia communication techniques, and more particular, to a method and system for handling multimedia calls.
2. Background of the Invention
The third-generation (3G) mobile communication systems are highlighted by the video service defined in the protocol of narrow-band low-rate multimedia communication architecture (H.324M). Along with the continuing development of next-generation networks (NGN) and IP multimedia networks, it has become a pressing issue to make a user terminal of a 3G system (hereinafter referred to as 3G terminal) and an IP multimedia terminal of an IP multimedia network able to inter-work in the video service. The IP multimedia terminal includes a terminal of IP-based multimedia communication architecture protocol (H.323) or a terminal based on the Session Initiation Protocol (SIP), i.e., a SIP multimedia terminal. Usually, a video inter-work conversion device is specially an equipment, e.g., a video gateway (VIG), used for implementing the inter-working between a 3G terminal (e.g. a mobile phone with H.324M video function) and an IP multimedia terminal in video service or speech service. FIG. 1 is a schematic diagram illustrating the inter-working between a 3G terminal and an H.323 terminal.
When an IP multimedia terminal initiates a multimedia call to a 3G terminal, the IP multimedia terminal calls the VIG first, and the VIG will initiate a multimedia call to the 3G terminal. The multimedia call in this application for patent refers to a call which complies with the H.324M protocol at 3G network. Compared with a speech call, a multimedia call includes the multimedia capability and is customarily referred to as a video call. If a 3G terminal is located in an area in which the H.324M video service is not supported due to roaming, network quality, or other reasons, the multimedia call that the VIG initiates to the 3G terminal will not be successful in the situation, i.e., the IP multimedia terminal will be unable to set up a multimedia call to the 3G terminal. In this case, as the H.324M video service is a circuit switched data services, the 3G network does not provide the service with a ring back tone and call failure tone during a dialing process, i.e., if the call fails, the calling user at the IP multimedia terminal is unable to have any prompt information of failure. From the viewpoint of use by a subscriber, the approach mentioned above will bring inconvenience to a subscriber of the H.324M video service, for example, a subscriber, when unable to learn that a call has failed, will wait blindly for the call to be put through or initiate the call request repeatedly, which will make the subscriber greatly unsatisfied with the H.324M video service.